Methionine is a sulfur-containing, essential amino acid, which is utilized in a variety of applications in the food and medical industries. For example, methionine is used as an additive in animal feed and foods and as an ingredient in many medicines. Accordingly, there is a high industrial demand for methionine.
To meet the high demand, methionine has been manufactured synthetically via a complex chemical synthesis involving hard-to-handle raw materials such as methyl mercaptan, propylene and hydrogen cyanide. The synthetic production of methionine requires harsh production environments or results in environmentally detrimental byproducts.
Due to the high cost of the starting materials and the environmental impact of synthetic production, a method of producing methionine by fermentation would be preferred. However, efficient fermentative production of methionine has been complicated by the presence of the sulfur atom in methionine. In addition, current fermentation methods utilize sugars and carbohydrates as a starting carbon source. The use of carbohydrates is complicated by finding reliable source material for year-round production and environmental concerns. As an example, many carbohydrate waste sources (e.g., residual crop biomass) can be fermented, but are seasonal. Alternately, some crops can be grown to produce carbohydrates for industrial fermentation reaction. However, these methods reduce the available arable land for food production and are expensive.
Given the high demand for methionine and the relative high cost and unreliability of fermentable carbohydrates, there is a need in the art for alternative and improved methods for biologically producing methionine in a cost-effective manner. The present disclosure meets such needs, and further provides other related advantages.